The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

MAGNET - MARK-MARK P.S.
Start: 23-Jun-2007
End: 04-Nov-2020
Blewitt, Geoff, Hammond, William C., Kreemer, Corne, 2009, MAGNET - MARK-MARK P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5CF9N8K